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Forensic chemistry literature has grown exponentially, with many analytical techniques being used to provide valuable information to help solve criminal cases. Among them, matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), particularly MALDI MS imaging (MALDI MSI), has shown much potential in forensic applications. Due to its high specificity, MALDI MSI can analyze a wide variety of compounds in complex samples without extensive sample preparation, providing chemical profiles and spatial distributions of given analyte(s). This review introduces MALDI MS(I) to forensic scientists with a focus on its basic principles and the applications of MALDI MS(I) to the analysis of fingerprints, drugs of abuse, and their metabolites in hair, medicine samples, animal tissues, and inks in documents.

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Lysergic acid diethylamide (LSD) and two phenethylamine classes (NBOHs and NBOMes) are the main illicit drugs found in seized blotter papers. The preliminary identification of these substances is of great interest for forensic analysis. In this context, this work constitutes the inaugural demonstration of an efficient methodology for the selective detection of LSD, NBOHs, and NBOMes, utilizing a fully 3D-printed electrochemical double cell (3D-EDC). This novel 3D-EDC enables the use of two working electrodes and/or two supporting electrolytes (at different pHs) in the same detection system, with the possibility of shared or individual auxiliary and pseudo-reference electrodes. Thus, the selective voltammetric detection of these substances is proposed using two elegant strategies: (i) utilizing the same 3D-EDC platform with two working electrodes (boron-doped diamond (BDD) and 3D-printed graphite), and (ii) employing two pH levels (4.0 and 12.0) with 3D-printed graphite electrode. This comprehensive framework facilitates a fast, robust, and uncomplicated electrochemical analysis. Moreover, this configuration enables a rapid and sensitive detection of LSD, NBOHs, and NBOMes in seized samples, and can also provide quantitative analysis. The proposed method showed good stability of the electrochemical response with RSD <9 % for Ip and <5 % for Ep, evaluating all oxidation processes observed for studied analytes (n = 7) at two pH levels, using the same and different (n = 3) working electrodes. It demonstrates a broad linear range (20-100 and 20-70 µmol L-1) and a low LOD (1.0 µmol L-1) for quantification of a model molecule (LSD) at the two pHs studied. Hence, the 3D-EDC combined with voltammetric techniques using BDD and 3D-printed graphite electrodes on the same platform, or only with this last sensor at two pH values, provide a practical and robust avenue for preliminary identification of NBOHs, NBOMes, and LSD. This method embodies ease, swiftness, cost-efficiency, robustness, and selectivity as an on-site screening tool for forensic analysis.

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The advent of miniaturized NIR instruments, also known as compact, portable, or handheld, is revolutionizing how technology can be employed in forensics. In-field analysis becomes feasible and affordable with these new instruments, and a series of methods has been developed to provide the police and official agents with objective, easy-to-use, tailored, and accurate qualitative and quantitative forensic results. This work discusses the main aspects and presents a comprehensive and critical review of compact NIR spectrophotometers associated with analytical protocols to produce information on forensic matters.

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A comprehensive data set of ecstasy samples containing MDMA (N-methyl-3,4-methylenedioxyamphetamine) and MDA (3,4-methylenedioxyamphetamine) seized by the Brazilian Federal Police was characterized using spectral data obtained by a compact, low-cost, near-infrared Fourier-transform based spectrophotometer. Qualitative and quantitative characterization was accomplished using soft independent modeling of class analogy (SIMCA), linear discriminant analysis (LDA) classification, discriminating partial least square (PLS-DA), and regression models based on partial least square (PLS). By applying chemometric analysis, a protocol can be proposed for the in-field screening of seized ecstasy samples. The validation led to an efficiency superior to 96 % for ecstasy classification and estimating total actives, MDMA, and MDA content in the samples with a root mean square error of validation of 4.4, 4.2, and 2.7 % (m/m), respectively. The feasibility and drawbacks of the NIR technology applied to ecstasy characterization and the compromise between false positives and false negatives rate achieved by the classification models are discussed and a new approach to improve the classification robustness was proposed considering the forensic context.

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3',4'-Methylenedioxy-N-tert-butylcathinone (MDPT), also known as tBuONE or D-Tertylone, is a synthetic cathinone (SC) frequently abused for recreational purposes due to its potent stimulant effects and similarity to illegal substances like methamphetamine and ecstasy. The structural diversity and rapid introduction of new SC analogs to the market poses significant challenges for law enforcement and analytical methods for preliminary screening of illicit drugs. In this work, we present, for the first time, the electrochemical detection of MDPT using screen-printed electrodes modified with carbon nanofibers (SPE-CNF). MDPT exhibited three electrochemical processes (two oxidations and one reduction) on SPE-CNF. The proposed method for MDPT detection was optimized in 0.2 mol L-1 Britton-Robinson buffer solution at pH 10.0 using differential pulse voltammetry (DPV). The SPE-CNF showed a high stability for electrochemical responses of all redox processes of MDPT using the same or different electrodes, with relative standard deviations less than 4.7% and 1.5% (N = 3) for peak currents and peak potentials, respectively. Moreover, the proposed method provided a wide linear range for MDPT determination (0.90-112 µmol L-1) with low LOD (0.26 µmol L-1). Interference studies for two common adulterants, caffeine and paracetamol, and ten other illicit drugs, including amphetamine-like compounds and different SCs, showed that the proposed sensor is highly selective for the preliminarily identification of MDPT in seized forensic samples. Therefore, SPE-CNF with DPV can be successfully applied as a fast and simple screening method for MDPT identification in forensic analysis, addressing the significant challenges posed by the structural diversity of SCs.

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This paper reports the use of paper spray mass spectrometry (PS-MS) combined with chemometric models to analyze seized samples of anabolic steroids. Because many forensic laboratories typically demand high-throughput analysis for this type of sample, we developed a quicker and simpler alternative analytical method for routine analysis with minimal sample preparation. Oily samples (n = 39) resulting from seizures carried out by Brazilian Federal and State Police units were selected for this study. These samples were analyzed by PS-MS in the positive ion mode and full scan (50-1000 m/z), providing spectra containing patterns of the respective active ingredients present in each product. A principal component analysis (PCA) model was built, which discriminated samples mainly according to their active ingredients and allowed to detect and characterize some cases of product counterfeiting. The variable selection method ordered predictors selection was employed jointly with PCA to improve sample cluster separation and to provide model simplification. The final PCA model was built with three principal components and using only 28 spectral variables. This model accounted for 69.82% of the variance and discriminated samples according to their specific active ingredients.

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Objective: This paper studies the integrity of the vote counting system in Brazil. Method: We analyze data from the Superior Electoral Court (TSE) for the 2018 Brazilian presidential election to assess suspicious vote count patterns deploying five techniques commonly used to detect fraud: a) the second-digit Benford's law test; b) the last digit mean; c) frequency analysis of last digits 0 and 5; d) correlation between the percentage of votes and the turnout rate; and e) resampled Kernel density of the proportion of votes. Results: The results show that the second-digit distributions for the three most voted candidates - Jair Messias Bolsonaro (PSL), Fernando Haddad (PT), and Ciro Gomes (PDT) - conform to Benford's law. We also find that last digit means and last digit frequency are within normal parameters, indicating no irregularities. Similarly, the fingerprint plot indicates a correlation coefficient that is consistent with the theoretical expectation of a fair election. The resampled Kernel density suggests that the vote count was performed without statistically significant distortions. These results are robust at different levels of data aggregation (polling station and municipality). Conclusion: The joint application of digit-focused tests, regression-based techniques, and patterns in the distribution of vote-shares provide a more reliable method for detecting anomalous cases. Relying on this unified framework, we find no evidence of electoral fraud in the 2018 Brazilian presidential election. These results advance our current understanding of statistical forensics tools and may be easily replicated to examine electoral integrity in other countries.

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A recent case of contamination of some batches of a Brazilian beer brand with diethylene glycol (DEG) had great repercussion, resulting in at least seven deaths. In this article, a direct method was developed for the rapid detection of DEG in beer samples based on portable near-infrared spectroscopy combined with partial least squares discriminant analysis (PLS-DA). The discriminant model was built with 100 uncontaminated beer samples and 100 samples containing DEG in a concentration range between 10 and 1000 mg L-1, totalizing 200 samples of different brands and styles. The method was validated by estimating figures of merit, such as false positive and false negative rates, sensitivity, specificity, accuracy, accordance, and concordance. The decision limit (CCα) of the method was 52 mg L-1 and the detection capability (CCß) was 106 mg L-1. This method does not consume reagents/solvents and can be suitable for the beer industry quality control or forensic investigations.

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Currently the great majority of the criminal acts have involved the use of firearms, for these reasons the evidences generate from these are one of the fundamental pillars of a forensic investigation. The firearm leaves evidence known as gunshot residue (GSR), which is principally composed of burnt and unburnt particles from the detonation, as well as fragments of the bullet, cartridge case, and the firearm. Gunshot residue (GSR) is produced when a firearm is discharged and large quantities of it can be transferred to an individual who has fired. SEM-EDX is the common technique used in the forensic laboratories, the analysis consists in detecting the particles and its elements. In this work we propose the use of X-ray Spectrometry by Total Reflection (TXRF) for the analysis of metals present in related samples in ballistic cases. The analysis was focused in the relationship of three elements present in GSR. A series of experiments with different persons firing gun of 9 mm was performed in a shooting range. Analytical XRFS signals corresponding to K line of Copper and L lines Barium and Lead were employed as the best discriminating variables. Machine Learning techniques, such as discriminant analysis, supported vector machines and partial least squares - discriminant analysis, enable the correct classification of all samples analyzed. A hundred samples were analyzed so far, this method has demonstrated a very high classification performance for detecting gunpowder residues in the skin.

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An electroanalytical method for determining dienestrol (DNL) in bovine urine samples is described. A glassy carbon electrode (GCE) modified with silver nanoparticles and functionalized multi-walled carbon nanotubes was used as working sensor. The modified GCE displays substantial analytical improvements including an amplified signal, fast electron transfer kinetics, and resistance to fouling. The irreversible oxidation signal of DNL is pH-dependent. Best reactivity is found at pH 3.0, where a typical anodic peak is recorded at 0.8 V (vs. Ag/AgCl). Square-wave voltammetry revealed a 8.4 nM detection limit (1.9 µg L-1), good repeatability and reproducibility (RSDs <5.0%), and good accuracy (93.2-99.4% recovery from spiked samples). The modified electrode is highly stable even in the presence of ions (Na+ and K+), urea and uric acid. The electrochemical sensor fulfills all requisites to be used as forensic device in surveillance of illegal livestock practices. Graphical abstract Schematic presentation of the construction of a glassy carbon electrode modified with silver nanoparticles and functionalized multi-walled carbon nanotubes. This sensor exhibited a remarkable performance for voltammetric detection of the illicit growth promoter dienestrol in animal urine.

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Schiff bases and their transition metal complexes are inexpensive and easy to synthesize. These compounds display several structural and electronic features that allow their application in numerous research fields. Over the last three decades, electroanalytical scientists of various areas have developed electrochemical sensors from many compounds. The present review discusses the applicability of Schiff bases, their transition metal complexes and new materials containing these compounds as electrode modifiers in sensors to detect analytes of forensic, pharmaceutical and environmental interest. In forensic sciences, Schiff bases are mainly used to analyze illicit drugs: chemical reactions involving Schiff bases can help to elucidate illicit drug production and to determine analytes in seized samples. In the environmental area, given that most methodologies provide Limit of Detection (LOD) values below the values recommended by regulatory agencies, Schiff bases constitute a promising strategy. As for pharmaceutical applications, Schiff bases represent an approach for analysis of complex biological samples containing low levels of the target analytes in the presence of a large quantity of interfering compounds. This review will show that new highly specific materials can be synthesized based on Schiff bases and applied in the pharmaceutical industry, toxicological studies, electrocatalysis and biosensors. Most literature papers have reported on Schiff bases combined with carbon paste to give a chemically modified electrode that is easy and inexpensive to produce and which displays specific and selective sensing capacity for different applications.

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Several new psychoactive substances (NPS) have reached the illegal drug market in recent years, and ecstasy-like tablets are one of the forms affected by this change. Cathinones and tryptamines have increasingly been found in ecstasy-like seized samples as well as other amphetamine type stimulants. A presumptive method for identifying different drugs in seized ecstasy tablets (n=92) using ATR-FTIR (attenuated total reflectance - Fourier transform infrared spectroscopy) and PLS-DA (partial least squares discriminant analysis) was developed. A hierarchical strategy of sequential modeling was performed with PLS-DA. The main model discriminated four classes: 5-MeO-MIPT, methylenedioxyamphetamines (MDMA and MDA), methamphetamine, and cathinones. Two submodels were built to identify drugs present in MDs and cathinones classes. Models were validated through the estimate of figures of merit. The average reliability rate (RLR) of the main model was 96.8% and accordance (ACC) was 100%. For the submodels, RLR and ACC were 100%. The reliability of the models was corroborated through their spectral interpretation. Thus, spectral assignments were performed by associating informative vectors of each specific modeled class to the respective drugs. The developed method is simple, fast, and can be applied to the forensic laboratory routine, leading to objective results reports useful for forensic scientists and law enforcement.

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A direct method based on the application of paper spray mass spectrometry (PS-MS) combined with a chemometric supervised method (partial least square discriminant analysis, PLS-DA) was developed and applied to the discrimination of authentic and counterfeit samples of blended Scottish whiskies. The developed methodology employed the negative ion mode MS, included 44 authentic whiskies from diverse brands and batches and 44 counterfeit samples of the same brands seized during operations of the Brazilian Federal Police, totalizing 88 samples. An exploratory principal component analysis (PCA) model showed a reasonable discrimination of the counterfeit whiskies in PC2. In spite of the samples heterogeneity, a robust, reliable and accurate PLS-DA model was generated and validated, which was able to correctly classify the samples with nearly 100% success rate. The use of PS-MS also allowed the identification of the main marker compounds associated with each type of sample analyzed: authentic or counterfeit.

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This article describes the use of paper spray mass spectrometry (PS-MS) for the direct analysis of black ink writings made with ballpoint pens. The novel approach was developed in a forensic context by first performing the classification of commercially available ballpoint pens according to their brands. Six of the most commonly worldwide utilized brands (Bic, Paper Mate, Faber Castell, Pentel, Compactor, and Pilot) were differentiated according to their characteristic chemical patterns obtained by PS-MS. MS on the negative ion mode at a mass range of m/z 100-1000 allowed prompt discrimination just by visual inspection. On the other hand, the concept of relative ion intensity (RII) and the analysis at other mass ranges were necessary for the differentiation using the positive ion mode. PS-MS combined with partial least squares (PLS) was utilized to monitor changes on the ink chemical composition after light exposure (artificial aging studies). The PLS model was optimized by variable selection, which allowed the identification of the most influencing ions on the degradation process. The feasibility of the method on forensic investigations was also demonstrated in three different applications: (1) analysis of overlapped fresh ink lines, (2) analysis of old inks from archived documents, and (3) detection of alterations (simulated forgeries) performed on archived documents. Graphical Abstract ᅟ.

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Polymorphic genetic markers located on the X chromosome might become a complement in particular forensic identification when the biological kinship are deficient. We analyzed forensic statistical parameters of 33 X-chromosome InDel polymorphisms in a sample of 320 individuals from Argentina. The X-chromosome InDel polymorphism (X-InDel) panel was amplified in a single multiplex PCR reaction. Hardy-Weinberg Equilibrium was determined in the female cohort, whereas the male cohort was used to calculate linkage disequilibrium (LD) tested by an extension of Fisher's exact test, D', and Chi-square values. Regarding LD, 15 markers were organized and grouped into six blocks containing two or three linked loci each, namely block I (MID356-MID357), block II (MID448804-MID3703-MID218), block III (MID3705-MID3706-MID304737), block IV (MID197147-MID3754), block V (MID3664-MID284601-MID103547), and block VI (MID3763-MID3728). The haplotype diversity was higher than 0.99 in all cases. Blocks III and VI showed the highest match probability in the studied population, whereas block II showed the lowest. The accumulated power of discrimination was 99.9999991 % in women and 99.9992925 % in men. The mean exclusion chance in trios and duos were 99.9891736 and 99.6099391 %, respectively. Since 15 markers are associated as haplotypic blocks, for a conservative treatment of the data, statistical evaluation should consider their haplotypic frequencies and the remaining 18 markers can be evaluated as independent loci.

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Paper spray mass spectrometry (PS-MS) combined with partial least squares discriminant analysis (PLS-DA) was applied for the first time in a forensic context to a fast and effective differentiation of beers. Eight different brands of American standard lager beers produced by four different breweries (141 samples from 55 batches) were studied with the aim at performing a differentiation according to their market prices. The three leader brands in the Brazilian beer market, which have been subject to fraud, were modeled as the higher-price class, while the five brands most used for counterfeiting were modeled as the lower-price class. Parameters affecting the paper spray ionization were examined and optimized. The best MS signal stability and intensity was obtained while using the positive ion mode, with PS(+) mass spectra characterized by intense pairs of signals corresponding to sodium and potassium adducts of malto-oligosaccharides. Discrimination was not apparent neither by using visual inspection nor principal component analysis (PCA). However, supervised classification models provided high rates of sensitivity and specificity. A PLS-DA model using full scan mass spectra were improved by variable selection with ordered predictors selection (OPS), providing 100% of reliability rate and reducing the number of variables from 1701 to 60. This model was interpreted by detecting fifteen variables as the most significant VIP (variable importance in projection) scores, which were therefore considered diagnostic ions for this type of beer counterfeit.

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Concerns about meat authenticity are increasing recently, due to great fraud scandals. This paper analysed real samples (43 adulterated and 12 controls) originated from criminal networks dismantled by the Brazilian Police. This fraud consisted of injecting solutions of non-meat ingredients (NaCl, phosphates, carrageenan, maltodextrin) in bovine meat, aiming to increase its water holding capacity. Five physico-chemical variables were determined, protein, ash, chloride, sodium, phosphate. Additionally, infrared spectra were recorded. Supervised classification PLS-DA models were built with each data set individually, but the best model was obtained with data fusion, correctly detecting 91% of the adulterated samples. From this model, a variable selection based on the highest VIPscores was performed and a new data fusion model was built with only one chemical variable, providing slightly lower predictions, but a good cost/performance ratio. Finally, some of the selected infrared bands were specifically associated to the presence of adulterants NaCl, tripolyphosphate and carrageenan.

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The aim of this study is to report a scavenging event, involving the consumption of a nurse shark, Ginglymostoma cirratum, by tiger sharks, Galeocerdo cuvier, at Fernando de Noronha archipelago, Brazil. Recreational divers found and photographed a bitten nurse shark carcass, just after sighting two tiger sharks near of the site. We estimated the sharks total lengths and discussed aspects of this feeding interaction using of images of forensic analysis. A straight cut on the nurse shark caudal fin, whose total length was estimated as 200 cm, suggest that it was caught by illegal fishing. A skin peeling process on the nurse shark fins indicates that the tiger sharks consumed it after its death, in a scavenging event. This is the first published report of a scavenging event involving the consumption of an elasmobranch by tiger sharks, allowing a better comprehension of tiger sharks' alimentary biology.

El objetivo de este estudio es reportar un evento de necrofagia que involucra el consumo de un tiburón nodriza (Ginglymostoma cirratum) por tiburones tigre (Galeocerdo cuvier) en el archipiélago de Fernando de Noronha, Brazil. Buzos aficionados encontraron y fotografiaron los restos mordidos de un tiburón nodriza, justo después de ver a dos tiburones tigre cerca del lugar. Mediante el análisis forense de imágenes estimamos la longitud total de los tiburones, y discutimos aspectos de esta interacción alimenticia. Una cortada recta en la aleta caudal del tiburón nodriza, cuya longitud total se estimó en 200 cm, sugiere que fue objeto de pesca ilegal. El desprendimiento de la piel observado en las aletas del tiburón nodriza indica que los tiburones tigre lo consumieron después de su muerte, en un evento de necrofagia. Este es el primer reporte publicado de un evento de necrofagia que involucra el consumo de un elasmobranquio por tiburones tigre, lo cual permite una mejor comprensión de su biología alimentaria.

O objetivo deste estudo é relatar um evento de necrofagia, envolvendo o consumo de um tubarão lixa, Ginglymostoma cirratum, por tubarões tigres, Galeocerdo cuvier, no arquipélago de Fernando de Noronha, Brasil. Mergulhadores recreativos encontraram e fotografaram uma carcaca de tubarão lixa com marcas de mordida, logo após avistarem dois tubarões tigres no mesmo local. A análise forense das imagens permitiu estimar o comprimento total dos tubarões, bem como discutir aspectos desta interacão alimentar. Um corte reto na nadadeira caudal do tubarão lixa, cujo comprimento total foi estimado em 200 cm, sugere que ele foi vítima da pesca ilegal. A descamacão das nadadeiras indica que o tubarão lixa foi consumido pelos tubarões tigres depois de morto, em um evento de necrofagia. Este é o primeiro reporte publicado de necrofagia de um elasmobránquio por tubarões tigres, contribuindo para a compreensão de sua biologia alimentar.

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In situations where the skeletal remains found are too fragmented, it is necessary to assess the human origin of such remains; for this purpose, various parameters are used, both anatomical and histological. The objective of the present study is to evaluate the various histomorphometric parameters to differentiate human from non-human bones, to further construct discriminatory functions that allow interspecies classification. Tibia bones sections from human, bovine, pig, hen, cat, and dog species were used, processed through conventional histological techniques and observed under the microscope with a 40x magnification, analyzing the Haversian Canal Density parameters by mm2, Diameter of the Haversian Canal and the Diameter of the Haversian System which were compared through one way ANOVA with Scheffé post test, p<0.05. Subsequently, the discriminatory functions were constructed for each species and the percentage of well-diagnosed cases was determined. Meaningful differences were found in the parameters analyzed; the discriminatory functions allowed to correctly classify 88.5 percent of the cases. Our results suggest that it is possible to differentiate human skeletal remains from non-human through the observation of their histological characteristics and histomorphometric parameters, but interspecies differentiation requires a more complex analysis...

En situaciones donde los restos óseos que se encuentran están muy fragmentados, es necesario evaluar el origen humano de dichos restos, para ello se utilizan diversos parámetros morfológicos tanto anatómicos como histológicos. El propósito de este estudio fue evaluar los distintos parámetros histomorfométricos para diferenciar hueso humano de no humano, para posteriormente construir las funciones discriminantes que permitan la clasificación interespecies. Se utilizaron secciones de hueso de tibia de individuos de especies: humano, bovino, cerdo, gallina, gato y perro, procesadas mediante técnica histológica convencional y observadas al microscópio con aumento 40x, analizándose los parámetros Densidad del canal de Havers por mm2, Diámetro del canal de Havers y diámetro del sistema Haversiano, los cuales fueron comparados mediante one way ANOVA con Scheffé post test con p<0,05. Posteriormente se construyeron las funciones discriminantes para cada especie y se determinó el porcentaje de casos bien diagnosticados. Se encontraron diferencias significativas en los parámetros analizados, las funciones discriminantes permitieron la correcta clasificación del 88,5 por ciento de los casos. Nuestros resultados sugieren que es posible diferenciar restos óseos humanos de no humanos mediante la observación de sus características histológicas y parámetros histomorfométricos, pero la diferenciación interespecie requiere de análisis más complejo...

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Observation of sexual chromatin has shown to be very helpful in gender forensic diagnosis. In the present study we analyzed the diagnosis performance of the method in, non-treated or treated with conventional bone techniques, exhumed bone pieces. We used long bones of male and female individuals, the method applied is described in Suazo et al. (2010). In the non-treated exhumed pieces, the general accuracy of the method was 75 percent, while in the treated pieces the method was inapplicable due to the lack of cells in the tissue. Our results suggest that it is possible to determine the sex of aged human bones buried under different conditions through a fast and simple histological method, but the treatment with physical and chemical means eliminates the remaining cells in the bone tissue.

La observación de la cromatina sexual ha demostrado ser útil en el diagnóstico forense del sexo. En este estudio analizamos el rendimiento diagnóstico del método en piezas óseas exhumadas no tratadas y tratadas mediante osteotécnica convencional. Utilizamos muestras de huesos largos de individuos de sexo masculino y femenino, el método se aplicó de acuerdo a lo descrito por Suazo et al., (2010). En las piezas exhumadas no tratadas la exactitud general del método fue del 75 por ciento, mientras que en las piezas tratadas el método resultó inaplicable, debido a la ausencia de células en el tejido. Nuestros resultados sugieren que es posible determinar el sexo en osamentas humanas exhumadas de larga data y en diferentes condiciones de enterramiento, mediante un método histológico rápido y sencillo, pero que el tratamiento por medios físicos y químicos elimina las células remanentes en el tejido óseo.

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